RIP "the Little Guy"

Sounds like stress to me.  Can you do water tests and let us know the results?  Usually if it's water problems the neons would be the first to go though.  I would recommend antibiotics for treatment but without finding what's causing the issue it'll fix the symptoms but not the cause.

As mad as it might sound, I've just done another water change - couldn't sleep for thinking "what if"... though I'm not sure the fish really appreciated me interrupting nap time.

Now should be on 60% ish water change in least 2 days, did a normal water change on Saturday of about 20% ish then too.  So that side of things *should* be OK.  I've removed some decaying plant matter I found lodged behaving the filter and permanently have the air stone switched on now. Also raised the temperature slightly and moved heater into better flow... looks ugly but that doesn't matter right now...

Any other suggestions out there? Do you think increasing temperature is the right move?

I'm glad @marquismirage that you were also of the view that medication wasn't the right call at the moment, to be honest I was too but just feeling guilty about things...  thanks for your swift reply

Thanks @fcmf .  Again my views are same as yours -ill continue to do 10-15% "non-invasive" water changes...

I think it is stress... I found her lying on some wood near the filter outlet breathing heavily.  Ill do another water change tonight... a big one...

If I take water to MA will they test it reliably for me?

(The temperature seemed low in there this morning so I've ramped up the heater.)

 

If you get your water tested at MA, watch to see if they use the paper-based test strips (like mine does) or liquid-based tests. The former doesn't test for ammonia. Ask specifically if they can test for ammonia, nitrite and nitrates, and ask for the actual results plus the name of the test kit. That way, we can interpret the results for you more if need be.

The results will only be valid at the date and time they're done, though, so I do hope Santa brings you a test kit on his visit tomorrow night. 

I also tend to run air stones in these circumstances.

Although not a necessity in a quarantine/hospital tank many people will use one as extra oxygen in the water can help if the cause of the illness was low oxygen amounts in the water column.  In a planted tank it'll reduce CO2 in the water column so be aware that an air stone will not be good for them.  But fish first is my opinion.

GBR's are so sensitive to water conditions.  Given that you removed some decaying plant matter I'm willing to bet that it caused an ammonia spike.  Hopefully we're getting closer to the root cause. 

Sorry to hear the sad news @Matt. You tried so hard to keep her going.
Unfortunately things don't seem to make sense when one fish is so ill and the others seem fine, and I'm afraid I can't offer any explanation.
Sometimes I think it would be easier to just keep fish and admire them, but it's impossible not to get attached to them. We are not industrial fish breeders, they are our pets, and feel a bond with them, and responsible for them...and that makes it difficult when one is seriously ill and doesn't make it.
My thoughts are with you and your gang.

Damn, sorry about your GBR. 

The test strips are accurate enough to keep track of what is happening with your tank. I strated out with the API test strips, but as I got more tanks I found it more cost effective to moce to the API master test kit. Buying from Amazon is cheaper than buying from LFS, and it lasts for ages.
Test strips are very quick and easy to use though, so there are times that I wish I could still use them on my tanks, as it takes me quite a long time to test them all.

I have a couple of the filters you mention. I think they originally came with some of the tanks when I bought them. I was worried that some of my more acrobatic fish my jump into the top, so those filters now reside in my axolotl tanks, and are still going strong. 

I don't have enough experience to comment on changing the filter, but I'm sure that the others will be able to give advice. 

Hi Matt,

This filter looks very similar to the Marina i110 which I have. (I may replace it shortly but put those plans on hold when it decided to start functioning well, typically just after I'd made the decision to replace it!)

The Marina filter which I have contains/contained a plastic grid and a filter cartridge comprising filter wool 'packets' filled with carbon and zeolite. Once the filter wool cartridges became saturated, the flow reduced and the advice on the packaging was that these required replaced at this stage - but that the plastic grid would contain the beneficial bacteria. In essence, the filter cartridges would have required replacing every few weeks.

Following advice on here, I kept the plastic grid part of the filter but dismantled the filter wool cartridges by cutting the filter wool as close to the plastic casing surrounding it (quite tough to do), scraping away all the carbon and zeolite pieces (very messy), and then wrapping the filter wool round some new filter sponge which I cut to size to fit in the space which had previously housed the filter cartridge, so that the filter wool would transfer/multiply the beneficial bacteria on it across/onto to the sponge.

The advantage of this is that the filter cartridges don't need replaced when they become clogged, and, more importantly, they don't need removed if I have to dose medication (due to the carbon being in them). It also means that, theoretically, if I had to set up a quarantine tank, I could just remove some of the sponge from the filter into another filter rather than having to use new, uncycled filter media - as it happens, though, I have two filters in my tank, so would remove one of those filters if I had to set up a QT.

Hope that helps, if indeed your filter is as similar to mine as I think it is.